The present invention relates to an apparatus and method for cleaning eggs.
There are four key aspects involved in virtually all egg cleaning operations. The four aspects are physical action, chemical action, temperature and time. While eggs can be soiled with virtually anything they come in contact with, the primary soils of concern are blood and feces. Prior to the establishment of large commercial egg cleaning operations, eggs were cleaned on farms, quite often with lye soap (sodium tallowate), water, and a small brush. The brush accomplished most of the removal physically. With the advent of compounded detergents the soap was replaced by detergents with formulas similar to 1 and 2 below.
12Ingredient%%Alkyl benzene sulfonate1515Sodium silicate77Sodium tripolyphosphate3035Sodium pyrophosphate5—Sodium carbonate4330Sodium sulfate—13100%100%
Such products were more effective than plain lye soap by virtue of superior wetting agents, higher alkalinity, and incorporation of builders like sodium tripolyphosphate into the formulas. With this change, the chemical aspect became a more significant aspect of the entire egg cleaning operation.
As centralized commercial egg cleaning operations developed, automatic egg washing machines came upon the scene. Such machines used pressurized water sprayed on the eggs to improve the physical aspect of soil removal. Under these conditions, the current egg cleaning formulas were not acceptable because the high foaming alkyl benzene sulfonate surfactants resulted in large amounts of foam flowing out of these machines. Nionic surfactants had to be substituted for the high foaming alkyl benzene sulfonate surfactants.
This was really when commercially compounded egg wash formulas became popular, because up until the development of automated egg washing machines standard off the shelf laundry detergents could be used quite effectively to clean eggs.
Formulas such as 3 and 4 shown below could be used in automatic machines.
34Ingredients%%Triton CF544—Antarox BL330—4Sodium silicate77Sodium tripolyphosphate3030Sodium pyrophosphate55Sodium carbonate3434Sodium sulfate2020100100
Subsequently, it was determined that small amounts of sodium hypochlorite were quite effective at removing some soils, especially protein based soils such as albumin as well as blood and feces. Accordingly, some compounders made products containing powdered sodium hypochlorite doners such as sodium dichloro isocyanurate known commercially as ACL 60 and CDB 63. Several such formulas are shown below. (formulas 5-8)
5678Ingredients%%%%Triton CF544—4—Antarox BL330—4—4Sodium Silicate7777Sodium tripolyphosphate34343434Sodium cab bonate32323232Sodium sulfate20202020ACL 603—3—CDB 63—3—3100100100100
With the advent of phosphate bans and limitations as well as cost pressures on large centralized commercial egg washing plants, compounders began selling both liquid and powered products based on caustic, sodium gluconate, and surfactants in the case of powders. Unfortunately surfactants cannot be coupled into highly concentrated caustic liquids because of the exceptionally high salt content. Several such powered and liquid products are shown below. (formulas 9-14)
Powdered9101112Ingredient%%%%Sodium carbonate5—5—Sodium tripolyphosphate—5—5Antarox BL 33011——Triton CF 54——11Caustic bead94949494100100100100Liquid1314Ingredient%%Caustic 50%9896Gluconic Acid 50%24100100
Liquid products do not contain surfactants, and while some egg cleaning operations use these relatively inexpensive formulas, the lack of surfactant is a performance weakness. Some plants add surfactant manually. However, concentrations are very difficult to control since water is continually being added and removed from the machines during operation.
The strength of powdered formulas such as 9-12 is that they are complete formulas and have all the necessary ingredients for optimum performance. The weaknesses are that as powders, they are difficult to dispense quantitatively and cannot be used effectively with a detergent sensing controller. In addition, caustic bead is a more expensive source of alkali than 50% liquid caustic because of the energy required to remove the water.
The strength of the liquid formulas is that the alkali source is 50% commodity caustic, which is the most economical source of alkali known. In addition, they can be easily dispensed quantitatively and thus can be used in conjunction with a detergent sensing controller. Their weakness is that they are not complete products because they do not contain effective wetting agents.
These formulas, when properly used, have proved reasonably effective in many plants. The sodium gluconate is a builder used to sequester calcium and improve the performance of the detergent. However, these products were not designed for egg washing. They were used because they were reasonably effective and very inexpensive.
They were originally designed as bottle washing cleaners and boil out compounds used for cleaning large stainless steel groens in food processing plants. The typical use concentrations were 1-2% (10,000-20,000 ppm). Sodium gluconate is a highly effective builder in 1-2% caustic solutions with a calcium stability complex of over 20. However, at egg washing ph's 10-11 the calcium stability complex falls to 2-3. Good effective builders have calcium stability complexes of 6 minimum. Thus sodium gluconate is virtually ineffective in egg washing operations.
In addition, these formulations are used at much lower levels in egg washing (about 2,000 ppm in egg washing versus 20,000 ppm in bottle washing or boil out compounds).
Thus in egg washing applications, there would be about 40 ppm of sodium gluconate verses 400 ppm of sodium gulconate in bottle washing or boil out applications. The point is that formation of the sodium gluconate calcium complexes is a stochiometric reaction and even if sodium gluconate did effectively sequester calcium in egg washing formulations it would only handle 1.6 grains of hardness which is much less then the water hardness of most egg washing operations.
On the other hand, bottle washing and boil out applications where sodium gluconate is very effective can handle 13 grains of water hardness.
Finally, sodium gluconate forms a soluble calcium complex. This prevents calcium from reacting with CO2 in the wash water and forming calcium carbonate spots and films which are easily noticed on glass and stainless surfaces. When calcium carbonate films or spots form on egg surfaces which are made of calcium carbonate and are opaque to start with, they are not visible so less objectionable.
Based on the aforementioned discussion and the fact that caustic/gluconate formulas have been shown effective in many egg washing operations, commodity caustic can be used in egg washing applications with equal performance to caustic/gluconate formulas. In both cases a low foaming wetting agent is required for optimum performance.
The low foaming wetting agent Applicants feel is the optimum product for egg washing is a product supplied by BASF known as Pluronic 25R2. This is a reverse pluronic block polymer. The center of the polymer is comprised of water soluble polyoxyethylene. The ends are capped with oil soluble polyoxypropylene which gives it its low foaming properties that are so important for egg washing operations. It is also highly effective at reducing the surface tension of water, thus providing excellent wetting properties.
While there are other low foaming wetting agents which are comparable to Pluronic 25R2 the type of wetting agent is not as critical as getting the correct concentration in egg washing machines. Low foaming wetting agents cannot be incorporated in 50% caustic solutions because they are not soluble in high salt solutions. Thus it is necessary to add the low foaming wetting agents independently. This is further complicated by the fact that low foaming wetting agents are organic and nonconductive in nature. Thus they cannot be dispended via a conductivity sensing system.
Most large egg washing machines are continuous cleaning machines. In order to run continuously, water must be replaced on a continuous basis in order to keep the soil load low enough for effective cleaning. This is accomplished by spraying fresh rinse water containing sodium hypochlorite sanitizer over the eggs in the final phase of the cleaning procedure. This fresh rinse water flows off the eggs and into the tank containing the wash water. Old dirty wash water flows through the opening of a standpipe located at the opposite end of the wash water tank. As a result, the detergent in the wash water is continuously being depleted because it is going down the standpipe and ultimately down the drain with the dirty water. Since detergents are primarily electrolytes, conductivity is proportional to the amount of detergent in the wash water. In continuous wash systems this principle can be used to maintain the proper detergent concentration. This can be done by inserting a two-pronged probe in the wash water tank, putting a voltage across the probes, and measuring conductivity. When the conductivity decreases below a certain level and indicates a low detergent concentration, the signal goes to a pc board which activates the detergent pump until the conductivity indicates the desired detergent concentration is achieved and the pump is deactivated.
Such systems have been tried in egg washing machines but have not been able to survive the environment for more than a few hours because the probes become coated with calcium, albumin, and other soils which render them ineffective. However, similar systems based on a fully enclosed inductance coil in lieu of an electronic probe have been shown to be highly effective at measuring detergent concentrations in the environment of egg washing machines.
Empty drum alarms are often based on a float switch at the bottom of the drum probe. These are not always trouble-free, sometimes sticking and failing to activate, thus requiring replacement from time to time. In addition, they may require that cumbersome wiring be attached to the drum probe.
There is a need for an automatic egg washing apparatus that overcomes these problems.